Method and apparatus for ocular perfusion

ABSTRACT

Ocular perfusion during intraocular surgery of the anterior or posterior ocular cavity is optimized through the method of using a gas pump having a discernible and controllable output pressure to pressurize a reservoir of liquid infusate, which is supplied under pressure to a surgical infusion instrument for perfusion of the selected ocular chamber (Gas Forced Liquid Infusion, GFLI). The infusate selection and the infusate pressure can be controlled with a high degree of accuracy and both can be rapidly varied by audible command. Preferentially a human sensible indication of pressure is constantly available at the gas pump.

This is a continuation of application Ser. No. 07/197,567 filed May 23,1988, now U.S. Pat. No. 4,900,301, which is a continuation-in-part ofSer. No. 07/099,533 filed Sept. 22, 1987, U.S Pat. No. 4,813,927.

FIELD OF THE INVENTION

The present invention relates generally to apparatus and methods used insurgery conducted on the eye. More particularly, the present inventionrelates to apparatus used in continuous infusion processes associatedwith such surgery. In even greater particularity, the present inventionrelates to apparatus for accurately and rapidly controlling the infusionpressure of the eye and rapidly converting between liquid and gasinfusion during such surgery.

BACKGROUND OF THE INVENTION

Intraoperative control of intraocular infusion pressure is an importantparameter in eye surgery. Liquid pressure regulation has beenaccomplished in most part using gravity-fed systems involving therelative height of the infusion bottle above the eye. A discussion ofthe development of gas infusion may be found in "Vitreous Microsurgery"by Steven Charles, M.D. in Williams & Wilkins, 1981, volume 4. As notedtherein, there are known power injectors or pumps which are capable ofmaintaining an accurate intraocular pressure during air infusion, ascompared to manual syringe injection. Such devices have also beendeveloped wherein a microcompressor is used to produce an inflow of gasdependent upon intraocular pressure.

As these advances are made in gas infusion apparatus, a need exist forcontrolled intraocular infusion method and apparatus which wouldfacilitate the interchangeability of gas infusion and liquid infusionduring surgery on the posterior segment of the eye (vitrectomy).Additionally, during surgery on the anterior chamber of the eye(cataract extraction) the need exists for more accurate, surgeoncontrolled and monitored liquid infusion.

During cataract surgery, the most common operation performed in theUnited States, the surgeon views only the anterior chamber of the eye asshown in FIG. 5, having no method of simultaneously monitoring theposterior segment.

Since the anterior chamber is quite small, containing only 0.25cc ofliquid volume, small and momentary aspiration flow exceeding infusionrates will result in anterior chamber collapse, as shown in FIG. 5. Theconsequence of anterior chamber collapse is damage to thenonreproducible monolayer of cells (endothelium) which lines the innersurface of the cornea. Keeping it clear of fluid. This endothelialdamage can then result in clouding of the cornea, with the need forsubsequent cornea transplantation.

It is common for cataract surgeons to perform incomplete temporaryclosure of the surgical incision prior to irrigation/aspiration cataractcortex removal. A true "closed-eye" system is never achieved, andanterior chamber collapse in this condition is a sign of wound leakageof infusion liquids rather than of inadequate infusion pressure. Ifanterior chamber collapse is encountered, the wound should be checkedfor tightness.

The cataract surgeon's most common defense against perceived anteriorchamber collapse is increasing of infusion pressure by raising agravity-feed infusion bottle an estimated height above the eye as shownin FIG. 4. Note that gas is not commonly infused into the anteriorchamber in such surgery. In practice, bottle height is not measured, sothat actual pressure delivered to the eye is unknown, and is presumed tobe sufficient when anterior chamber collapse no longer occurs.

Unfortunately, corneal endothelial damage may also occur as a result ofhigh infusate volume or jetstream mechanical damage from the use of highflow rates under high pressure. These effects, moreover, are not readilyapparent to the surgeon due to his inability to perceive the flow rateor pressure. Retinal artery occlusion may also occur, invisible to thesurgeon and resulting in blindness. Finally iris prolapse through thewound may occur as a result of excessive infusion pressure.

Ideally, cataract irrigation/aspiration surgery should be performed withnormal ocular pressure (25 mm Hg). Failing this, infusion pressureshould be raised as little as possible to maintain anterior chamberpressure to avoid collapse during active irrigation/aspiration. Becauseunnecessarily high infusion pressure and flow rates can injure retinaland corneal tissues with little warning to the surgeon, increasinginfusion to the eye should be the last solution attempted to remedyanterior chamber collapse. As previously stated, the surgeon shouldfirst check adequate wound closure. Further, even with an adequatelyclosed eye, anterior chamber collapse may occur as a result ofundisciplined, continuous, high rate aspirations. High vacuum aspirationis necessary to achieve cataract removal, but successful removal ofblocks of cataract cortex bottle provides pressurized liquid forinfusion. The gas conduit and liquid conduit are preferentially formedas a dual-tube conduit and are connected to a stopcock which allows thephysician to select either gas infusion or liquid infusion.

In an alternate embodiment, adapted for anterior chamber surgery, thegas infusion line is eliminated since gas infusion is not commonly usedin this type surgery; the flexible conduit connections between theliquid infusate bottle and the eye, and between the gas pressure deviceand the liquid infusate bottle are maintained. In both embodiments, theoutput of the gas pump is connected directly to the pressurized gaspocket above the infusion liquid via a conduit extending within theliquid infusion bottle

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatus embodying features of our invention are depicted in theappended drawings which form a portion of this invention and wherein:

FIG. 1 is a perspective view showing the apparatus as used duringsurgery;

FIG. 2 is a broken lay-out view showing the invention not in use;

FIG. 3 is a broken lay-out view showing the cataract surgery embodiment;

FIG. 4 shows the prior art and ocular structures; and

FIG. 5 shows an instance of ocular collapse.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 4 illustrates the common control methodology and apparatus forluquid infusion of the eye as heretofore used in cataract and invitreous surgery. FIG. 5 is illustrative of common ocular collapse whenusing the method and apparatus shown in FIG. 4.

Referring to the figures for a better understanding of the invention, itmay be seen that the invention is for use with a patient who is lyingbeneath surgical drapes 11 on an operating table 12. A continuousinfusion air/gas pump 13 is located on an equipment stand 14 as isconventional practice. The output of the air/gas pump 13 is displayed asby LED's at digital display 16 so that the pressure generated therebymay be monitored by the surgery team and precisely controlled.

The output of the air/gas pump 13 is used to pressurize a liquidinfusion bottle 23 to provide Gas Forced Liquid Infusion (GFLI) of theeye. Use of Gas Forced Liquid Infusion (with digital numeric readout ofinfusion pressure in view of the surgeon) allows the surgeon for thefirst time to accurately and continuously monitor this most importantparameter. In this method, the infusion bottle is hung at eye height, sothat gravity feed, the preferred technique of the prior art, contributesno pressure to perfusion/infusion. Rather, total control of perfusionpressure is instead achieved by instilling in the infusate bottle, gasunder pressure, provided by the gas pump. The infusion pressure canthereby be meticulously and rapidly selected by the surgeon.

An antibacterial filter connector 17 attaches a flexible conduit 18 tothe pump 13 in any conventional manner as is well known in the art. Theconduit 18 extends from the equipment stand 14 to near an IV support 19and terminates in a T-connector 21 or other suitable device fordirecting the airflow from the pump 13 along two paths. A fluidpressurization conduit 22 is connected between the T-connector 21 and aliquid infusion bottle which has a sealing means 25 which allows thefluid pressurization conduit to extend through the sealing means intothe interior of the infusate bottle and seals the infusate bottle 23which is 23 supported by the IV support 19 and serves to pressurize thefluid therein in accordance with the output pressure of the pump 13.This fluid pressurization conduit extends within the infusion bottle soas to connect the gas volume above liquid with the gas pump for ventingpurposes. A fluid delivery conduit 24 is connected as the output ofinfusion bottle 23 and terminates as one input to infusate stopcockselection valve 26. An air delivery conduit 27 is connected between theremaining branch of the T-connector 21 an the valve 26. Note that valve26 may be a three-way input valve which would allow selection of eitherliquid, air, or finally an air/gas mixture (e.g. sulfur hexafluoride SF₆20%, perfluoropropane C₃ F₈ 15%) delivered by a second gas pump. Thevalve 26 has a single output to an infusion conduit 28 which isconnected to and supplies an eye infusion cannula 29.

As shown in FIG. 1, the infusion bottle 23 is placed at the patient'seye level so as to contribute no gravity infusion pressure as had beencustomary in the prior art. Air/gas is pumped into the bottle 23 viaconduits 18 and 22 to provide the desired infusion pressure. Although anormal starting pressure may be selected, it should be clear that theinfusion pressure can be rapidly changed by adjusting the outputpressure of the air pump 13. The air pump selected should have a digitaldisplay 16 of the pressure which should be visible to all operation roompersonnel. It has been determined that the displayed, conduit, andintraocular static pressures agree to within two to four mm of Hg usingthe present apparatus.

Valve 26 allows the surgical team to quickly switch from liquid infusionto gas infusion. Conduits 24 and 27 may be formed from the two halves ofa twin plastic tube, for example Dicoc Twin Bore Silicone IV tubing,such that the valve 26 may be located immediately proximal to the shortcannula 29, thereby minimizing the time and volume required to clearinfusion liquid from the system cannula 29 when gas is desired.

From the foregoing, it may be seen that we have provided an effectiveapparatus and method (Gas Forced Liquid Infusion, GFLI) which greatlyimproves the surgeon's efficiency in vitrectomy operations in whichliquid to gas infusion changes are desired and also provides a readilycontrollable means for varying the infusion pressure during all liquidinfusion eye surgery including cataract removal. As is well known, it ispossible to stop or reduce bleeding by raising the intraocular pressureto maximum known safe levels, usually 35 to 45 mm of Hg. Using thepresent invention with a digital display 16 allows the surgical team toquickly determine the infusion pressure levels and rapidly change thelevel as required, to maximum safe level with great accuracy.

It is the aspect of the invention that allows the surgical team tocontinuously monitor and precisely control the infusion pressure whichis of critical importance to the cataract surgeon. The tubing systemshown in FIG. 3 uses an antibacterial filter connector 31 to attach aflexible tubing 32 to the air pump 13. The flexible tubing 32 isconnected directly to the infusion bottle 23 which is supplied withinfusion liquid as shown in FIG. 2. A single flexible conduit 33 isprovided to carry pressurized infusion liquid from the bottle to a valve34 which controls the flow of liquid to the infusion/aspiration device36 used in cataract surgery. With the digital readout 16 available thesurgeon is able to constantly monitor the pressure being utilized in theeye and therefore is at all times aware of and alert to the potentialdeleterious consequences of overpressurization and jetstreaming. Thus,due to his ability to monitor and accurately select the intraocularpressure, the surgeon will naturally turn more attention to adequatewound closure and disciplined aspiration rather than using a potentiallydestructive infusion pressure level to prevent ocular collapse.

The use of the gas pump 13 to pressurize the infusion bottle 23 ineither of the embodiments above also leads to a significant furtherrefinement in the art. Voice recognition technology can be used toregulate the output pressure of the gas pump 13. Thus, an inputmicrophone 37 is connected to a voice recognition circuit, many of whichare commercially available, which in turn outputs a control signal tothe pump 13. Preferentially the pump will be provided with a speaker 38which will enunciate the pressure, subsequent to an instruction tochange pressure or upon a query by the surgeon; or upon a variance ofthe pressure outside a predetermined tolerance. The surgeon's voice maybe specifically recognized so that he might state the desired pressurein an audible voice, and the machine would respond immediately that itwill seek the commanded pressure after a preset safety delay, in theabsence of further commands. Infusate selector valve 26 may also bevoice actuated. For the first time, perfusion pressure to the eye andinfusate source can be controlled directly by the surgeon rather thannecessitating the presence of other operating room personnel. Immediatepressure adjustment with voice response completes surgeon control ofinfusion pressure--the most vital parameter characterizing "closed-eye"surgery.

While we have shown our invention in two forms, it will be obvious tothose skilled in the art that it is not so limited but is susceptible ofvarious changes and modifications without departing from the spiritthereof.

What we claim is:
 1. Apparatus for controlling the intraocular pressureduring closed wound intraocular surgery consisting essentially of:(a) agas pump having a variable output pressure; (b) a liquid infusatereservoir operatively connected to said gas pump to receive pressurizedgas therefrom such that liquid infusate in said reservoir is pressurizedin accordance with the output pressure of said gas pump, with saidreservoir confining both said liquid infusate and a volume of gas indirect communication with said gas pump; and (c) an ocular surgicalinfusion instrument operatively connected to said liquid infusatereservoir to receive infusate therefrom.
 2. A connector for use incombination with a gas pump having a variable output pressure, a gasoutlet, and a liquid infusate reservoir containing an infusate, and anocular surgical infusion instrument, comprising:(a) a first flexibleconduit operatively connected at one end thereof to the outlet of saidgas pump; (b) sealing means operatively connected to a second end ofsaid first flexible conduit to provide gaseous communication between theinterior of said reservoir and said first flexible conduit and forsealing said reservoir; (c) an infusate outlet port located in saidsealing means through which liquid infusate is discharged from saidreservoir; and (d) second flexible conduit operatively connected to saidinfusate outlet port at one end and in communication with said infusioninstrument at a second end, wherein said first and second flexibleconduits define a closed system interconnected between said gas pump andsaid infusion instrument.
 3. A connector as defined in claim 2 furthercomprising an antibacterial filter operatively connected intermediatesaid first flexible conduit and said gas pump.
 4. A connector as definedin claim 3 further comprising a valve operatively connected between saidinfusion instrument and said second flexible conduit for regulating theflow of infusate to said instrument.
 5. A connector as defined in claim2 wherein said first and second flexible conduits comprise lengths offlexible silicon tubing.
 6. Apparatus for providing gas forced liquidinfusion to a selected anterior or posterior ocular chambercomprising:(a) a gas pump having a variable pressure output, selectivelyvariable over a predetermined range of pressures encountered inintraocular surgery; (b) a reservoir containing a liquid infusate; (c) aconduit member including a microbacterial filler, connected directlyfrom the output of said gas pump to said reservoir to pressurize theliquid infusate in said reservoir; (d) a second conduit memberoperatively connected between said reservoir and an intraocular surgicalinstrument for delivery of the liquid infusate under pressure to the eyeof a patient undergoing surgery; and (e) human sensible means forindicating the pressure in the eye during intraocular surgery. 7.Apparatus as defined in claim 3 wherein said human sensible means is avisible digital display showing the current output pressure of the pump.8. A method of ocular perfusion using Gas Forced Liquid Infusion (GFLI)comprising:(a) supplying pressurized gas to a selected output pressurefrom a gas pump; (b) pressurizing the contents of a liquid infusatebottle with the output pressure of said gas pump; (c) supplying thecontents of said liquid infusate bottle to a surgical infusioninstrument for infusion into a selected anterior or posterior ocularchamber as infusate; (d) selectively varying the pressure of theinfusate within the ocular chamber by controlling the output pressure ofsaid gas pump; and (e) providing a human sensible indication of thepressure within the eye wherein said human sensible indicator of theoutput pressure is a visual signal indicating the output pressure of thepump.